Cracking hydrocarbon oil



Aug. 1, 1939. v. STAPLETN 2,168,074

CIRACKING HYDROCARBON OIL Filed 001;. 25, 1935 INVENTOR v V/CTO? STAPLET/V FLA... w. bww

ATTORNEY Patented Aug. 1, 1939 A .l

UNITED STATES PATENT OFFICE CRACKING HYDROCARBON OIL Victor Stapleton; New York, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application october 2,5, 1935, serial No. 46,642

ls claims. (o1. 19e- 58) Thisinvention relates to the art of cracking substantial accumulation of liquid therein, while hydrocarbon oil wherein higher boiling hydrothe vapors are subjectedto prolonged conversion carbons are converted into lower boiling products treatment at a temperature sufficiently high to and pertains more particularly to a method of and produce high-grade anti-knock gasoline.

ij, apparatus for merging highly heated streams of When operating in this manner it was found, 5 hydrocarbon. products. contrary to what might be expected, that less While my invention has a more general applicoking troubles were encountered and longer cation it has been found to have particular adoperating runs were realized than was the case vantages when used in a process of cracking hywhen only clean condensate stocks were sub- .lQ drocarbon oil of the general nature disclosed in jected to cracking treatment without admixture an earlier co-pending application, Serial No. with heavier black oil. j 24,794, led jointly by myself and Claude E. Wat- With the use of only lighter, vaporizable stocks son. f t in the treatment troubles developed in the region lIt is the natural desiderata of all oil-cracking ofv the tar outlet from the reaction chamber. 1 5 processes to produce the maximum yield of the This was surprising in view of the fact that heavy 15 best quality gasoline from the raw charging stock black oil contains constituents unvaporizable in the most economical manner. The increase in under conditions obtaining within the reaction compression ratio of internal combustion motors chamber and which normally have a greater has necessitated the placing of more emphasis on tendency to form coke than the more volatile oil. the quality and particularly the non-detonating AWhile it was found that coking troubles in this or anti-knock properties of the gasoline produced. region of .the reaction chamber were avoided 2o It is a demonstrated fact that gasolines prowhen admixing heavy black oil containing unduced as a result of high-temperature, high crack vaporizable constituents with the cracked vapor per pass cracking operations have,as a general products passing to the reaction chamber so as rule, materially better non-detonating ycharacto maintain a condition of liquidity in the region 25 teristics than gasoline resulting from simple disof the tar outlet from the chamber, other coking tillation or from low-temperature cracking treattroubles at times developed in the transfer line ment. In view of this, the trend is to avoid between the point -of merger of the black oil cracking at low temperatures insofar as possible. stream with the highly heated products from the To meet present day requirements in this respect cracking coil and the reaction chamber. While 30 it is usually considered desirable to carry out the these troubles dolnot always develop at this point cracking reaction at temperatures upwards of it has been encountered at times'when operating 850 F., for example. on certain Mid-Continent crude stocks, for eX- There are, however, certain heavy black oil ample. In some cases a ring of coke was found to stocks which are susceptible to cracking, such as have formed immediately adjacent the 00111160- 35 cracked or crude residuals, but which, because of tion joining the two streams and in other cases at their tendency to form troublesome coke deposits other points on the down-stream side of the conwithin the equipment, are not amenable to highnection. temperature cracking treatment in the normal While the reason for the formation of coke in 40 manner by being passed through a tubular coil this region of the transfer line has not been 40 in a heating zone. definitely established, I have reason to believe In'the application above identied filed jointly that it is due to alternate drying and wetting of by myself and Claude E. Watson there is dethe pipe surface by the products passing therescribed a method of cracking wherein these heavy through.l When the connecting pipes are joined black oils are rapidly heated toy high cracking to each other by a simple connection such as by 45 temperature by direct admiXture with more higha T or Y connection the twoy streams do not inly heated cracked products from a tubular heatstantly become thoroughly mixed so that the ing coil employed for high temperature cracking surface of the pipe line immediately adjacent the of a relatively cleaner stock such as gas oil. The connection on the down-stream side and at other admixed products are passed to an enlarged repoints in the transfer line may be washed with 50' action chamber wherein the vapors separate from relatively dry kvapors from the heating coil durunvaporized liquid residuum. The liquid residing one instant of time and with a relatively cooluum, after being subjected to high-temperature er and heavierv liquid from the other stream at cracking for only a relatively short time is reother times.` This alternate wetting andvdrying moved from the chamber without allowing any of the surface of the pipe is believed to be the 55 cause of the building up of the coke ring at this point in the line.

The object of the present invention is to provide a method of and an apparatus for merging the two streams of oil hereinbefore described so as to avoid coking difficulty within this region.

According to my invention a heavy black oil stream containing constituents unvaporizable under conditions obtaining within the reaction chamber is caused to merge with more highly heated products from a cracking coil in a specially constructed connection wherein the two streams are caused to rst pass in concentric relation to each other for a short time, and the outer concentric stream is then caused to be deflected into the inner stream to effect a rapid and intimate mixture thereof.

Further, in accordance with my invention, it is preferred to mount this specially constructed connection directly at the point of entrance into the reaction chamber so that the two streams, after being intimately mixed, pass directly into the chamber without passing through an additional pipe line. In accordance with this preferred form the relatively cooler black oil stream is passed in outer concentric relation to the more highly heated products from the heating zone so that the metal wall of the chamber surrounding the connections is maintained at the temperature of the cooler stream rather than at the higher temperature of the products from the heating zone, and localized stresses in this region of the vessel are avoided.

Further objects and advantages of my invention will become apparent from the more detailed description hereinafter in which reference will be made to the accompanying drawing.

In the drawing Figure l is a diagrammatic illustration of an oil-cracking apparatus for carrying out a process of the general nature hereinbe' fore described, and Figure 2 is a detailed sectional View of the special connection for merging the two oil streams.

Referring to Figure 1 of the drawing, a relatively clean vaporizable stock is passed through a tubular heating coil I located within the furnace II, and the hot cracked products from the heating coil I0 are then passed through the transfer line I2 to a connection I3 wherein they are merged with a relatively cooler black oil stream from the line I4. The combined stream of oil then passes into the reaction chamber I5 wherein further conversion is attained. The charging stock for the cracking coil I may consist in whole or in part of a condensate stock such as Mid-Continent gas oil from an eX- traneous source introduced into the system through line I6 or may consist in whole or in part of reflux condensate formed in the process as hereinafter described. The black oil stream may comprise a residual stock such as crude or reduced crude or other heavy fractions preferably containing constituents unvaporizable under conditions obtaining in the reaction chamber I5. This stock, preferably preheated to a temperature of the order of 600 to 800 F., may be introduced directly into the line I 4 through connection I'I, or may be a product of the process hereinafter described or a mixture of both.

As shown in Figure 2 the end of the pipe I2 carrying the hot products from the heating coil projects downwardly into an enlarged sleeve I8 which in turn extends through an opening in the wall of the reaction chamber I5 and is welded to the surrounding wall of the reaction chamber to form a pressure-tight seal. 'I'he sleeve I8 is of somewhat larger diameter than the pipe I2 throughout the greater portion of its length to form an annular space into which the cooler black oil stream from the pipe I4 discharges. The outer end of the sleeve I8 is of reduced diameter to t tightly around the pipe I2 and is welded thereto by means of plug welds I9 and a. circumferential fillet weld 20 to form a fluidtight seal. The inner end of the sleeve I3 extends somewhat beyond the end of the pipe I2 and is flared inwardly to form an annular nozzle for projecting the outer black oil stream into the central stream of highly heated products from the heating coil.

By merging the two streams directly at the point of entrance into the reaction chamber so as to effect a. rapid and thorough intermixture of the two streams in the manner hereinbefore described the black oil stream may be rapidly heated to a relatively high cracking temperature suflicient to effect a high rate of cracking per pass and produce high grade anti-knock gasoline with minimum cracking of this stock in the lowtemperature range,

The unvaporizable constituents of the heavy black oil and any liquid polymers which may be formed during lthe cracking of the lighter condensate immediately separate from the vapors upon being introduced into the reaction chamber and drop to the bottom of the reaction chamber and are withdrawn therefrom through line 2I at a rate which will prevent a substantial accumulation of liquid being formed therein. In addition to subjecting the black oil to short time cracking at high temperature the unvaporizable constituents thereof perform an important function of maintaining a condition of liquidity in the region of outlet 2| and serve to reduce coking troubles within this region of the chamber.

Moreover, by passing the black oil stream through the connection in outer concentric relation to the more highly heated products from the cracking coil the vessel wall surrounding the sleeve is maintained at lower temperature, and differential stresses within this region of the vessel are avoided.

The liquid withdrawn from the bottom of the reaction chamber I5 through line 2i may be cooled and sent to storage or may be further distilled either by reduction in pressure or by additional heat or both, and the heat of the vapors liberated during the distillation may be employed directly or indirectly for preheating fresh heavy charge for the process all in a manner well known in the art and which, consequently, has not been shown on the drawing.

The vapors separated from the liquid within the reaction chamber I5, after being subjected to the desired conversion treatment at relatively high cracking temperature, such as upwards of 850 F., for example, within the chamber, are withdrawn therefrom through line 22 and pass to suitable fractionating equipment for separation into desired fractions.

While I have shown for purpose of illustration, and prefer a reaction chamber of the downflow type, wherein the vapors pass in a downward direction, it will be understood that an upflow type of chamber, or a plurality of chambers arranged in parallel or in series through which the vapors pass in the same or opposite directions may be employed.

Further, by way of illustration, I have shown the fractionating equipment for the cracked vapors `as comprising a primaryv fractionating tower 23 and a secondary fractionating tower 24 connected by vapor line 25. By having two fractionating zones the heavy charging stock, which preferablyl contains unvaporizable crude residuals such as crude or reduced crude and which may be preheated in any desired manner, such-as by direct or indirect contact constituents contained in the liquid withdrawn from the bottom of reaction chamber l5 through line 2|, as hereinbefore described, may be introduced into the primary fractionating tower 23 at an intermediate point thereof. In this event the bottoms from the primary fractionating tower may be passed through lines 26, 2l and pump 28 to line I4 and constitute a part or all of the heavy black oil stream merged with the products of the cracking coil in connection I3.

Clean condensate formed in the secondary fractionating tower is withdrawn therefrom through line 29, and may be passed through line 3D, pump 3| and line 32 to the heating coil I0 and constitute a part or all of the charging stock therefor.

Vapors remaining uncondensed in the secondary tower 24 may be passed through line 33 to a condenser 34 wherein the desired gasoline distillate from the process is condensed, and the prod'- ucts then pass to receiver 35 wherein the distillate separates from fixed gases in the customary manner.

As an example of temperature conditions which may be maintained in the cracking portion of the equipment, in order to realize the greatest advantages from my invention, the outlet of the heating coil may be held at a temperature upwards of 950 F. and preferably from 975 to 1000 F. or higher. The reaction chamber is preferably maintained upwards of 850 F. and preferably at from 860 F. to 925 F. The maximum temperatures maintained in this portion of the equipment as a practical matter are limited to temperatures suiliciently low to maintain a condition of liquidity in the bottom of the reaction chamber.

The amount of preheating of the black oil before merging with the products from the heating coil will depend upon the character of the stock and the manner and rate of heating. For example, when introducing crude or reduced crude into the primary fractionating tower and using the bottoms from the tower as the black oil stock, as shown in the drawing, and wherein the fresh oil is rapidly heated by direct contact with cracked vapors undergoing fractionation, the black oil may be preheated to a temperature as high as 800 F. providing the bottoms are not permitted to remain at this temperature for any substantial length of time. In this connection it will be understood that one of the objectives is to avoid low-temperature cracking in the process insofar as possible.

The pressure maintained on the cracking portion of the equipment, wherein my improvement lies, may vary over a relatively wide range. As a matter of practice it is usually desirable to maintain a superatmospheric pressure such as from 200 to 400 or more pounds4 per square inch so that velocity of ow of the products through the equipment may be more closely regulated. The reaction chamber may be maintained at substantially the same pressure as the outlet of the heating coil, except for the necessary drop to effect the desired flow, or a substantial differential pressure between the coil and reaction chamber may be maintained by a suitable reducing valve.

surewithin the reaction chamber is helpful in maintaining a condition of liquidity at the outletof the reaction chamber.

When operating in accordance with my invention, coking trouble in the transfer line on the downstream side of the connection, joiningthe; black oil stream and cracked products from the heating coil, has been completely avoided so that` in no case has coking in this region of the equipment limited the length of operating runs, whereas in certain cases, particularly when treating certain Mid-Continent crudes, coking in the transfer line has been the cause of premature discontinuance of the process in prior practices. of. this nature.

While my invention has been found to have particular advantage in the process before described, it may have other applications. Having thus described the preferred embodiment, it is understood that my invention embraces such other variations and modifications as come within the spirit and scope thereof and that it is not my intention to dedicate any novel features thereof or to limit the invention-except as necessary to distinguish from prior art.

I claim:

1. The method of cracking hydrocarbon oils, in an apparatus comprising a heating coil and a communicating enlarged reaction chamber, that comprises heating a condensate oil in transit through the heating coil to a high cracking temperature, delivering a stream of resultant highly heated products from said coil into the upper portion of said enlarged reaction chamber, combining a cooler stream of charging stock comprising residual constituents of crude petroleum with said stream of highly heated products in such manner that no restriction of the mixture occurs during or substantially after admixture by bringing they streams together directly at the point of entry of the same into said enlarged reaction chamber to thereby raise said charging stock to a desired cracking temperature, passing the commingled products downwardly in said reaction chamber while maintaining them at a cracking temperature under superatmospheric pressure and withdrawing liquid from the lower portion of the chamber at a rate adequate to prevent the accumulation of liquid therein.

2. The method of cracking hydrocarbon oils, in an apparatus comprising a heating coil and a communicating enlarged reaction chamber, that comprises heating a condensate oil in transit through the heating coil to a high cracking temperature, delivering a stream of resultant highly heated products from said coil into the upper portion of said enlarged reaction chamber, combining a cooler stream of charging stock comprising residual constituents of crude petroleum with said stream of highly heated products in such manner that no restriction of the mixture occurs during or substantially after admixture by bringing the streams together directly at the point of entry of the same into said enlarged reaction chamber to thereby raise said charging stock to a desired cracking temperature, passing the commingled products downwardly in said reaction chamber while maintaining them at av racking temperature under superatmospheric pressure, separately withdrawing vapors from a lower portion of said reaction chamber and separately withdrawing liquid from a point below that at which said vapors are withdrawn at a rate adequate to prevent accumulation of liquid However, a substantial superatmospheric prestherein.

3. The method of cracking hydrocarbon oils, in an apparatus comprising a heating coil and a communicating enlarged reaction chamber, that comprises heating a condensate oil in transit through the heating coil to a high cracking temperature, delivering a stream of resultant highly heated products from said coil into the upper portion of said enlarged reaction chamber, introducing a cooler stream of charging stock comprising residual constituents of crude petroleum into the upper portion of said enlarged reaction chamber and causing said stream of charging stock to oW in outer concentric relation to the stream of highly heated products from the heating coil While the streams are passing through the inlet opening in the wall of said reaction chamber and merging the two concentric streams in such manner that no restriction of the mixture occurs during or substantially after admixture by bringing the streams together directly at the point of entry into the reaction chamberto thereby raise said charging stock to a desired cracking temperature, passing the commlngled products downwardly in said reaction chamber While maintaining them at a cracking temperature under superatmospheric pressure and Withdrawing liquid from the lower portion of the chamber at a rate adequate to prevent the accumulation of liquid therein.

VICTOR STAPLETON. 

